diff --git a/cmd/tools/vtest-self.v b/cmd/tools/vtest-self.v
index c5151ddc8d..407076f5de 100644
--- a/cmd/tools/vtest-self.v
+++ b/cmd/tools/vtest-self.v
@@ -19,7 +19,7 @@ const (
 		'vlib/builtin/float_test.v',
 		'vlib/builtin/byte_test.v',
 		'vlib/builtin/rune_test.v',
-		'vlib/builtin/builtin_test.v',
+		'vlib/builtin/builtin_test.c.v',
 		'vlib/builtin/map_of_floats_test.v',
 		'vlib/builtin/string_int_test.v',
 		'vlib/builtin/utf8_test.v',
diff --git a/vlib/builtin/builtin_test.v b/vlib/builtin/builtin_test.c.v
similarity index 100%
rename from vlib/builtin/builtin_test.v
rename to vlib/builtin/builtin_test.c.v
diff --git a/vlib/builtin/wasm_bare/libc_impl.v b/vlib/builtin/wasm_bare/libc_impl.c.v
similarity index 100%
rename from vlib/builtin/wasm_bare/libc_impl.v
rename to vlib/builtin/wasm_bare/libc_impl.c.v